Genetic or pharmacological reduction of cholangiocyte senescence improves inflammation and fibrosis in the Mdr2-/- mouse

• Published in: JHEP reports 2021-06, Vol.3 (3), p.100250-100250, Article 100250
• Main Authors: Alsuraih, Mohammed, O’Hara, Steven P., Woodrum, Julie E., Pirius, Nicholas E., LaRusso, Nicholas F.
• Format: Article
• Language: English
• Subjects: Apoptosis resistance; Biliary epithelial cell; Cellular senescence; Cholestatic liver disease; Primary sclerosing cholangitis; Senescence-associated secretory phenotype; Senolytics
• ISSN: 2589-5559; 2589-5559
• DOI: 10.1016/j.jhepr.2021.100250

Cholangiocyte senescence is important in the pathogenesis of primary sclerosing cholangitis (PSC). We found that CDKN2A (p16), a cyclin-dependent kinase inhibitor and mediator of senescence, was increased in cholangiocytes of patients with PSC and from a PSC mouse model (multidrug resistance 2; Mdr2-/-). Given that recent data suggest that a reduction of senescent cells is beneficial in different diseases, we hypothesised that inhibition of cholangiocyte senescence would ameliorate disease in Mdr2-/- mice. We used 2 novel genetic murine models to reduce cholangiocyte senescence: (i) p16Ink4a apoptosis through targeted activation of caspase (INK-ATTAC)xMdr2-/-, in which the dimerizing molecule AP20187 promotes selective apoptotic removal of p16-expressing cells; and (ii) mice deficient in both p16 and Mdr2. Mdr2-/- mice were also treated with fisetin, a flavonoid molecule that selectively kills senescent cells. p16, p21, and inflammatory markers (tumour necrosis factor [TNF]-α, IL-1β, and monocyte chemoattractant protein-1 [MCP-1]) were measured by PCR, and hepatic fibrosis via a hydroxyproline assay and Sirius red staining. AP20187 treatment reduced p16 and p21 expression by ~35% and ~70% (p >0.05), respectively. Expression of inflammatory markers (TNF-α, IL-1β, and MCP-1) decreased (by 60%, 40%, and 60%, respectively), and fibrosis was reduced by ~60% (p >0.05). Similarly, p16-/-xMdr2-/- mice exhibited reduced p21 expression (70%), decreased expression of TNF-α, IL-1β (60%), and MCP-1 (65%) and reduced fibrosis (~50%) (p >0.05) compared with Mdr2-/- mice. Fisetin treatment reduced expression of p16 and p21 (80% and 90%, respectively), TNF-α (50%), IL-1β (50%), MCP-1 (70%), and fibrosis (60%) (p >0.05). Our data support a pathophysiological role of cholangiocyte senescence in the progression of PSC, and that targeted removal of senescent cholangiocytes is a plausible therapeutic approach. Primary sclerosing cholangitis is a fibroinflammatory, incurable biliary disease. We previously reported that biliary epithelial cell senescence (cell-cycle arrest and hypersecretion of profibrotic molecules) is an important phenotype in primary sclerosing cholangitis. Herein, we demonstrate that reducing the number of senescent cholangiocytes leads to a reduction in the expression of inflammatory, fibrotic, and senescence markers associated with the disease. [Display omitted] •p16 and p21 are major mediators of cellular senescence and are highly expressed in cholangiocyt